1. Field of the Invention
The present invention relates to internal combustion engines and methods and apparatus for improving the cold start-up of internal combustion engines.
2. Background of the Related Art
There are several problems that must be overcome during the start-up of an internal combustion engine that is cold. First, atomized or vaporous fuel in the air/fuel mixture introduced into the engine cylinders tends to condense onto the cold engine components, such as cylinder walls and the air intake rail, especially in compression ignition (CI) engines such as diesel engines. Condensed hydrocarbon fuels on engine cylinder walls may act as solvents that wash away desirable lubricant films resulting in excessive mechanical wear from reciprocating piston rings in sliding contact with the engine cylinder walls. The condensed mixture of fuel and lubricant is capable of passing the piston rings, entering the crankcase and contaminating the engine""s lubrication reservoir resulting in a loss of overall lubricant effectiveness and a further increase in mechanical wear, even during normal operation. Second, the condensation of atomized or vaporous fuels onto cold engine cylinder walls results in poor engine performance and delayed engine availability during and immediately after cold engine start-up. Engine availability is diminished during cold engine start-up due to poor lubricant properties at low temperatures, non-uniform fuel distribution and improper air/fuel mixtures. Third, if the vehicle is equipped with a catalytic converter increased levels of unwanted pollutants are emitted from the tailpipe for a period of about one to three minutes after cold engine start-up because that is the amount of time normally needed for the engine exhaust gases to heat the catalytic converter in the exhaust system to an efficient operating temperature.
The undesirable levels of pollutants released during and immediately after cold engine start-up present a problem of increasing importance. In order to meet increasingly strict governmental engine emission standards, a catalytic converter must be located in the exhaust stream of the engine. The conventional method of heating the catalytic converter to its efficient operating temperature is to heat the catalyst by passing high temperature exhaust gases from the engine through the catalyst. This exhaust gas heating, in conjunction with the exothermic nature of the oxidation reactions occurring at the catalyst, will usually bring the catalyst to an efficient operating temperature, or xe2x80x9clight-offxe2x80x9d temperature, in one to three minutes. However, until the catalyst light-off temperature is reached, the engine exhaust gasses pass through the catalytic converter relatively unchanged, and unacceptably high levels of pollutants such as carbon monoxide, hydrocarbons and nitrogen oxides are released into the atmosphere.
The elimination of excessive mechanical wear during cold engine start-up, poor engine performance during cold start-up, and the control and suppression of unwanted emissions created by cold start-up, are primary considerations for designers of internal combustion engines and manufacturers of chemical lubricants and fuel additives designed to alleviate these problems. A significant part of overall engine wear occurs during and immediately after cold start-ups, especially in diesel engines which are otherwise extremely durable due to the lubricating effect of diesel fuel at normal operating temperatures. A high percentage of the undesirable emissions or pollutants created by internal combustion engines equipped with catalytic converters occur during cold start-ups. Therefore, an apparatus and method is needed to prevent unwanted engine wear, to improve the operational availability of engines upon cold start-up, and to control and suppress undesirable levels of pollutants during cold start-up of combustion engines.
The problems of cold engine start-up can be addressed by leaving the engine running continuously, but the unwanted result of this method is excessive fuel consumption and related emissions. Various methods of adding heat energy to an internal combustion engine prior to or during start up have been proposed. These methods include adding heat energy to the engine crankcase, fuel, intake air or cylinder block before attempting to start the engine. Successful preheating systems include electrical resistance heating systems (including glow plugs, crankcase heaters and block heaters) and volatile and hydrocarbon based fuel burners. Acceptable methods of preheating are dictated by the availability and portability of the energy source, preheat time requirements and by safety concerns.
Electrical resistance heating is a common and successful method of adding heat energy to an internal combustion engine either prior to starting or after starting to bring the engine to operating temperature. Limitations of the equipment, however, affect the suitability of this method. The primary limitation on electrical preheating is the amount of electrical energy required by the heater. The typical automotive battery is not a practical source to supply the electrical power needed to preheat an internal combustion engine because the electrical load on the vehicle battery may exceed the rated battery output. In any event, the repeated electrical demand necessary for engine preheating in cold temperatures will unacceptably shorten the battery life of the typical automotive battery.
An alternative to battery powered electrical resistance heating has been to decrease the strain on the power supply by supplying the electrical power directly from an alternator after the engine has started rather than directly from the vehicle battery. This solution also has its shortcomings. First, the initial start-up of the engine to drive the alternator is necessarily done without preheating, resulting in excessive mechanical wear, unwanted pollutants and poor performance. Second, an alternator-powered electrical resistance heater still requires a substantial increase in battery capacity to cope with the start-up scenario. Even by supporting the engine heater with electrical power from an alternator, there is still a concern with respect to battery capacity because electric resistance heating will likely be needed for an extended period of time. In addition, the maximum alternator power output required by the system requires a complicated switching mechanism to shut down the heater once the engine achieves a suitable operating temperature and an increased alternator speed to 2,000 to 4,500 rpm during the heating period. There will also be an increased up-front automotive cost because the alternator must be oversized for typical automotive electrical power demand in order to support the heater during and after engine start-up.
To date, there has not been an automotive engine heating system which gives almost instantaneous heating of the engine components or intake air without the inherent drawbacks stated above. Thus, there remains a need for an improved system for preheating internal combustion engine components or intake oxygen or air that reduces excessive mechanical wear and poor engine performance and which minimizes undesirable emissions by accelerating the attainment of full engine and catalytic converter performance. Such a system must be simple and must not reduce the rated lifetime of the engine, the catalytic converter, or the battery and other electrical components of the vehicle.
The present invention provides a catalytic heating apparatus for reducing wear, reducing emissions and improving operational availability of a combustion engine. The apparatus heats combustion engine components and/or intake air to an engine and comprises: a catalyst; a source of hydrogen; a conduit connecting the source of hydrogen to the catalyst; a temperature sensor in the catalyst; a temperature sensor in the engine; and a means for controlling the introduction of hydrogen from the source of hydrogen to the catalyst based on a temperature sensed by the temperature sensors.
The present invention provides a method for reducing wear, reducing unwanted emissions and improving operational availability of a combustion engine comprising: disposing a hydrogen oxidation catalyst in the air intake line; catalytically combining hydrogen and oxygen on the catalyst to produce heat; and transferring the heat to the air by contacting the catalyst and by mixing the intake air with the gasses produced by the exothermic oxidation of hydrogen.